Fiber Bragg grating pressure sensor, manufacturing method and using method

Abstract

The invention discloses a fiber Bragg grating pressure sensor, a manufacturing method and a using method, the sensor comprises a shell structure, a diaphragm type structure is arranged in the shell structure, the shell structure is divided into a first cavity and a second cavity which are adjacent up and down, a first water inlet is formed in the top of the shell structure and is communicated with the first cavity, and a second water inlet is formed in the bottom of the shell structure and is communicated with the second cavity; one end of the equal-strength cantilever beam structure is arranged on the inner wall of the first cavity, the other end of the equal-strength cantilever beam structure overhangs and is located at the water inlet, the second water inlet is formed in the bottom of the shell structure and communicates with the second cavity, and the first fiber bragg grating assembly is arranged on the equal-strength cantilever beam structure and used for measuring the wave impact load. The second fiber bragg grating assembly is arranged on the diaphragm type structure and used for measuring hydrostatic pressure. The upper constant-strength cantilever beam structure is adopted to measure the wave impact load, and the lower diaphragm type structure is adopted to measure the hydrostatic pressure, so that the measurement precision and applicability of the sensor are improved, and monitoring in different use scenes is met.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a fiber Bragg grating pressure sensor and a manufacturing method and a use method thereof. Background Art

[0002] The study of wave loads on coastal and offshore structures mainly includes the study of the effects of regular and irregular waves on open-type buildings, single piles, pile groups, breakwaters, seabeds, and structure-pile-seabed interactions. In some related technologies, piezoresistive or piezoelectric high-frequency pressure sensors, or arrays of pressure sensors, are often used to study the normal and tangential forces of regular and irregular waves acting on vertical steel walls, inclined walls, and gravel breakwaters. In other related technologies, point load sensors, pressure sensors, and force balances are often used to measure wave forces. These sensors have the advantages of small inherent size, high inherent frequency, and wide frequency domain range, but are easily interfered by electromagnetic signals. At the same time, the corrosion protection problem of sensors also needs to be solved.

[0003] Furthermore, in flume experiments and field measurements, various pressure sensors are often used in related technologies to measure wave impact forces. Measuring wave loads through sensors requires sensors with large ranges, wide frequency response, excellent dynamic performance, corrosion resistance, and strong anti-electromagnetic interference capabilities. Pressure sensors used to measure wave impact forces have been greatly improved, but limited sensing areas or the large number of components required limit their practicality. Summary of the invention

[0004] The purpose of this application is to solve at least one of the technical problems existing in the prior art. To this end, this application proposes a fiber Bragg grating pressure sensor that can improve measurement accuracy and applicability, greatly improve monitoring efficiency, and meet the monitoring needs of different usage scenarios.

[0005] The present application also proposes a method for manufacturing the above-mentioned fiber Bragg grating pressure sensor.

[0006] The present application also proposes a method for using the above-mentioned fiber Bragg grating pressure sensor.

[0007] The fiber Bragg grating pressure sensor according to the first embodiment of the present application includes:

[0008] Shell structure;

[0009] A diaphragm structure, the diaphragm structure is arranged in the shell structure, and the diaphragm structure is used to divide the shell structure into a first cavity and a second cavity adjacent to each other in upper and lower directions;

[0010] a first water inlet, the first water inlet being arranged on the top of the housing structure and communicating with the first cavity;

[0011] An equal-strength cantilever beam structure, one end of which is arranged on the inner wall of the first cavity, and the other end of which is cantilevered and located at the first water inlet;

[0012] a second water inlet, the second water inlet being disposed at the bottom of the housing structure and communicating with the second cavity;

[0013] A first fiber Bragg grating component, wherein the first fiber Bragg grating component is arranged on the equal strength cantilever beam structure so that the first fiber Bragg grating component can be used to measure wave impact load;

[0014] A second fiber grating component is provided on the diaphragm structure so that the second fiber grating component can be used to measure hydrostatic pressure.

[0015] The fiber Bragg grating pressure sensor according to the first aspect of the present application has at least the following beneficial effects: an upper equal-strength cantilever beam structure is used to measure wave impact loads, and a lower diaphragm structure is used to measure hydrostatic pressure, thereby improving the measurement accuracy and applicability of the sensor, greatly improving the monitoring efficiency, and meeting the monitoring requirements of different usage scenarios. At the same time, the fiber Bragg grating has the advantages of corrosion resistance, high sensitivity, and strong anti-electromagnetic interference capability, and in conjunction with a high-speed optical demodulator, it can detect high-frequency signals of up to several kilohertz, and is suitable for use in the monitoring of wave impact loads.

[0016] According to the fiber Bragg grating pressure sensor described in the embodiment of the first aspect of the present application, the first fiber Bragg grating component includes a first optical fiber line and a first grating optical fiber FBG and a second grating optical fiber FBG arranged on the first optical fiber line, and the first optical fiber line is arranged on the equal-intensity cantilever beam structure so that the first grating optical fiber FBG is arranged close to the middle of the vertical center line of the equal-intensity cantilever beam structure, and the second grating optical fiber FBG is arranged close to one end of the equal-intensity cantilever beam structure.

[0017] According to the fiber Bragg grating pressure sensor described in the embodiment of the first aspect of the present application, a first lead-out port connected to the first cavity is formed on the shell structure, a groove extending along the vertical center line is formed on the equal-strength cantilever beam structure, and the first optical fiber is arranged in the groove and led out from the first lead-out port.

[0018] According to the fiber Bragg grating pressure sensor described in the embodiment of the first aspect of the present application, the other end of the equal-strength cantilever beam structure includes a cylindrical structure, the cross-sectional shape of the first water inlet is circular, and the cylindrical structure extends into the first water inlet and there is a gap between the cylindrical structure and the first water inlet.

[0019] According to the fiber Bragg grating pressure sensor described in the embodiment of the first aspect of the present application, the second fiber Bragg grating component includes a second optical fiber line and a third grating optical fiber FBG, a second lead-out port connected to the second cavity is formed on the shell structure, the third grating optical fiber FBG is arranged near the center of the diaphragm structure, and the second optical fiber line is connected to the third grating optical fiber FBG and is led out from the second lead-out port.

[0020] According to the fiber Bragg grating pressure sensor described in the embodiment of the first aspect of the present application, the shell structure includes a cover plate, an intermediate component and a bottom plate, the diaphragm structure serves as the bottom of the intermediate component, the intermediate component forms the first cavity and the top is used to be assembled with the cover plate, and the bottom of the intermediate component is used to be assembled with the bottom plate to enclose the second cavity.

[0021] According to the fiber Bragg grating pressure sensor described in the embodiment of the first aspect of the present application, a drainage port is provided on the side wall of the intermediate component.

[0022] According to the fiber Bragg grating pressure sensor described in the embodiment of the first aspect of the present application, a plurality of second water inlets are provided, and each of the second water inlets is distributed on the bottom plate in an array.

[0023] According to a method for manufacturing a fiber Bragg grating pressure sensor according to an embodiment of the second aspect of the present application, the method comprises the following steps:

[0024] Build a model through 3D software, and print the shell structure, diaphragm structure, and equal-strength cantilever beam structure through 3D printing;

[0025] Paste the first fiber grating assembly to the center of the upper surface of the equal-strength cantilever beam structure, and paste the second fiber grating assembly to the center of the lower surface of the diaphragm structure;

[0026] Leading the first fiber grating assembly and the second fiber grating assembly out of the housing structure;

[0027] The packaging process is performed to seal the inside of the device.

[0028] A method for using a fiber Bragg grating pressure sensor according to a third aspect of the present application includes the following steps:

[0029] The first fiber grating assembly includes a first optical fiber line and a first grating optical fiber FBG and a second grating optical fiber FBG arranged on the first optical fiber line, the first optical fiber line is arranged on the equal-intensity cantilever beam structure, so that the first grating optical fiber FBG is arranged close to the middle position of the vertical center line of the equal-intensity cantilever beam structure, and the second grating optical fiber FBG is arranged close to one end of the equal-intensity cantilever beam structure, the second fiber grating assembly includes a second optical fiber line and a third grating optical fiber FBG, the third grating optical fiber FBG is arranged close to the center position of the diaphragm structure, and the second optical fiber line is connected to the third grating optical fiber FBG;

[0030] Design principle based on fiber Bragg grating:

[0031]

[0032] Where λ is the initial wavelength of the fiber Bragg grating under strain-free conditions, Δλ is the drift of the fiber Bragg grating center wavelength caused by strain and temperature changes; P eff =0.22 is the photoelastic coefficient, α and ξ are the thermal expansion coefficient and thermo-optic coefficient of the fiber Bragg grating;

[0033] The principle of measuring wave impact load based on equal strength cantilever beam structure:

[0034] Theoretical formulas for equal strength beam structures include:

[0035] The uniformly distributed load on the structure is simplified to the concentrated force acting on the cylinder at the other end of the cantilever beam structure with equal strength, that is:

[0036] F=P×πr 2 #(2)

[0037] F is the equivalent value of the uniformly distributed load applied to the top of the cantilever beam, P is the surface pressure of the cylinder at the top of the cantilever beam, and r is the radius of the cylindrical sensing structure;

[0038] From material mechanics, we know that:

[0039]

[0040] M (x) =-F(Lx)#(4)

[0041]

[0042] According to the boundary conditions ω=0, ω′=0, we can get:

[0043] c1=c2=0

[0044]

[0045] Therefore, the free end deflection of the beam is:

[0046]

[0047] The strain on the beam is:

[0048]

[0049] In the above formula, L is the length of the beam, b is the width of the beam, h is the thickness of the beam, and E is the Young's modulus of the material;

[0050] Combining (1) and (6), the relationship between the hydrodynamic pressure and the FBG wavelength drift under external load is obtained as follows:

[0051]

[0052] So we can know the sensor sensitivity coefficient K PA for:

[0053]

[0054] According to mechanical theory, the radial strain generated at the center of a laterally unconstrained uniform diaphragm under the action of uniform external pressure P is expressed as:

[0055]

[0056] Where, E is the elastic modulus of the diaphragm in the vertical direction; v is the Poisson's ratio; h is the thickness of the diaphragm; R is the radius of the diaphragm;

[0057] The relationship between wavelength shift and hydrostatic pressure is expressed as follows:

[0058]

[0059] Therefore, when the room temperature is stable, the sensor sensitivity coefficient K PB for:

[0060]

[0061] The data measured by the second grating optical fiber FBG are used to perform temperature compensation on the data measured by the first grating optical fiber FBG and the third grating optical fiber FBG.

[0062] It is not difficult to understand that the method for manufacturing the fiber Bragg grating pressure sensor in the embodiment of the second aspect of the present application and the method for using the fiber Bragg grating pressure sensor in the embodiment of the second aspect of the present application both have the technical effects of the fiber Bragg grating pressure sensor in the embodiment of the first aspect described above, and therefore will not be described in detail.

[0063] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The present application is further described below with reference to the accompanying drawings and embodiments;

[0065] Figure 1 This is a schematic diagram of the structure of an embodiment of the present application;

[0066] Figure 2 A cross-sectional view of an embodiment of the present application;

[0067] Figure 3 An exploded diagram of an embodiment of the present application;

[0068] Figure 4 A schematic diagram of an intermediate component in an embodiment of the present application;

[0069] Figure 5 It is a schematic diagram of a medium-strength cantilever beam structure in an embodiment of the present application.

[0070] Reference numerals:

[0071] 100, shell structure; 101, first cavity; 102, second cavity; 110, cover plate; 111, first water inlet; 120, intermediate component; 121, diaphragm structure; 122, first outlet; 123, drain outlet; 130, bottom plate; 131, second water inlet; 132, second outlet;

[0072] 200, equal strength cantilever beam structure; 210, cylindrical structure; 220, groove;

[0073] 310, first optical fiber line; 320, first grating optical fiber FBG; 330, second grating optical fiber FBG;

[0074] 410, a second optical fiber line; 420, a third grating optical fiber FBG. DETAILED DESCRIPTION

[0075] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0076] In the description of the present application, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0077] In the description of this application, "several" means one or more, "more" means at least two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0078] In the description of this application, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this application after combining the specific content of the technical solution.

[0079] Reference Figures 1 to 5 The fiber Bragg grating pressure sensor of the first aspect of the present application specifically relates to a dynamic and static water pressure sensor based on a fiber Bragg grating. The fiber Bragg grating pressure sensor includes a shell structure 100, a diaphragm structure 121, an equal-strength cantilever beam structure 200, a first fiber Bragg grating component and a second fiber Bragg grating component.

[0080] The diaphragm structure 121 is arranged in the shell structure 100, and the diaphragm structure 121 is used to divide the shell structure 100 into a first cavity 101 and a second cavity 102 adjacent to each other in upper and lower directions. The first water inlet 111 is arranged at the top of the shell structure 100 and communicated with the first cavity 101. One end of the equal-strength cantilever beam structure 200 is arranged on the inner wall of the first cavity 101, and the other end of the equal-strength cantilever beam structure 200 is cantilevered and located at the first water inlet 111. The second water inlet 131 is arranged at the bottom of the shell structure 100 and communicated with the second cavity 102. The first fiber grating assembly is arranged on the equal-strength cantilever beam structure 200 so that the first fiber grating assembly can be used to measure wave impact loads. The second fiber grating assembly is arranged on the diaphragm structure 121 so that the second fiber grating assembly can be used to measure hydrostatic pressure.

[0081] It can be understood that the fiber Bragg grating pressure sensor of the present application uses an upper equal-strength cantilever beam structure 200 to measure wave impact loads, and a lower diaphragm structure 121 to measure hydrostatic pressure, which improves the measurement accuracy and applicability of the sensor, greatly improves the monitoring efficiency, and meets the monitoring of different usage scenarios. At the same time, the fiber Bragg grating has the advantages of corrosion resistance, high sensitivity, and strong anti-electromagnetic interference ability, and cooperates with a high-speed optical demodulator to detect high-frequency signals with a frequency of up to several kilohertz, which is suitable for application in the monitoring of wave impact loads. In some embodiments, the first cavity 101 is located above the second cavity 102, and the wave impact load can enter from the first water inlet 111 and act on the equal-strength cantilever beam structure 200, and cooperate with the first fiber Bragg grating component to measure the wave impact load. The second water inlet 131 is set at the bottom of the second cavity 102, and static water can enter from the second water inlet 131 when in use. The lower diaphragm structure 121 cooperates with the second fiber Bragg grating component to measure hydrostatic pressure.

[0082] In some embodiments of the present application, the first fiber Bragg grating assembly includes a first optical fiber line 310 and a first grating fiber FBG320 and a second grating fiber FBG330 arranged on the first optical fiber line 310. The first optical fiber line 310 is arranged on the equal-intensity cantilever beam structure 200, so that the first grating fiber FBG320 is arranged near the middle of the vertical center line of the equal-intensity cantilever beam structure 200, and the second grating fiber FBG330 is arranged near one end of the equal-intensity cantilever beam structure 200. It can be understood that the first grating fiber FBG320 and the second grating fiber FBG330 are arranged on the first optical fiber line 310 to form a fiber Bragg grating, and the second grating fiber FBG330 is arranged at a position where no displacement occurs, so that the first grating fiber FBG320 can be corrected with the second grating fiber FBG330 as a reference, thereby improving the test accuracy.

[0083] In some embodiments, the first grating fiber FBG320 is used to measure the center position of the equal-intensity cantilever beam structure 200 in the vertical direction. Therefore, the first grating fiber FBG320 is set near the middle of the vertical center line of the equal-intensity cantilever beam structure 200, and the detection point is adaptively adjusted to meet the measurement requirements.

[0084] In some embodiments of the present application, a first lead-out port 122 communicating with the first cavity 101 is formed on the housing structure 100, a groove 220 extending along the vertical center line is formed on the equal-strength cantilever beam structure 200, and the first optical fiber line 310 is arranged in the groove 220 and led out from the first lead-out port 122. It can be understood that the first lead-out port 122 facilitates the lead-out of the first optical fiber line 310 so that the sensor can work normally, and the groove 220 is used to limit the first optical fiber line 310 to prevent shaking due to external factors, and the groove 220 can also play a role in guiding the first optical fiber line 310 to be led out.

[0085] In some embodiments, a limit block or limit buckle may be further provided in the groove 220 to improve the limit effect. In some embodiments, the position of the first outlet 122 may be adaptively adjusted, and being provided near one end of the equal strength cantilever beam structure 200 may make the structural design more reasonable.

[0086] In some embodiments of the present application, the other end of the equal-strength cantilever beam structure 200 includes a cylindrical structure 210, the cross-sectional shape of the first water inlet 111 is circular, and the cylindrical structure 210 extends into the first water inlet 111 and there is a gap between the first water inlet 111. It can be understood that using the cylindrical structure 210 to sense wave impact loads can improve measurement accuracy and simplify the design process. The cross-sectional shape of the first water inlet 111 is adaptively adjusted in conjunction with the cylindrical structure 210, and the two are coordinated to accurately measure the wave impact load.

[0087] In some embodiments, the other end of the strength cantilever beam structure can be set to other structural shapes. In this case, the simplified formula of the uniformly distributed load on the structure can be adaptively adjusted according to the corresponding stress conditions of the structural shape, and the cross-sectional shape of the first water inlet 111 can be adaptively adjusted synchronously.

[0088] In some embodiments of the present application, the second fiber Bragg grating assembly includes a second optical fiber line 410 and a third grating optical fiber FBG420, a second lead-out port 132 communicating with the second cavity 102 is formed on the housing structure 100, the third grating optical fiber FBG420 is arranged near the center of the diaphragm-type structure 121, and the second optical fiber line 410 is connected to the third grating optical fiber FBG420 and is led out from the second lead-out port 132. It can be understood that the third grating optical fiber FBG420 is arranged on the second optical fiber line 410 to form a fiber Bragg grating, and the third grating optical fiber FBG420 is used to measure the center position of the diaphragm-type structure 121, so the third grating optical fiber FBG420 is arranged near the middle of the vertical center line of the equal-strength cantilever beam structure 200, and the detection point is adaptively adjusted to meet the measurement requirements and improve the test accuracy.

[0089] In some embodiments, the position of the second outlet 132 can be adaptively adjusted, and being disposed at a position close to the first outlet 122 can make the structural design more reasonable.

[0090] In some embodiments, based on the setting of the second grating fiber FBG330, the correction of the third grating fiber FBG420 can be performed based on the zero position of the second grating fiber FBG330. In other embodiments, the second fiber grating assembly can also include a grating fiber FBG that plays a zero position role to compensate for the third grating fiber FBG420 and improve the measurement accuracy.

[0091] In some embodiments of the present application, the housing structure 100 includes a cover plate 110, an intermediate component 120 and a bottom plate 130, the diaphragm structure 121 serves as the bottom of the intermediate component 120, the intermediate component 120 forms a first cavity 101 and the top is used to assemble with the cover plate 110, and the bottom of the intermediate component 120 is used to assemble with the bottom plate 130 to enclose a second cavity 102. It can be understood that the quality of the sensor can be guaranteed by making each component separately and packaging the structure after assembly, wherein the first cavity 101 is formed by the intermediate component 120, and the diaphragm structure 121 serves as the bottom of the intermediate component 120 and encloses the second cavity 102 with the bottom plate 130, so that the diaphragm structure 121 is located between the first cavity 101 and the second cavity 102, and the sensor can simultaneously measure the wave impact force and the hydrostatic pressure, and the cantilever beam structure is used to measure the wave impact load, and the diaphragm structure 121 is used to measure the hydrostatic pressure.

[0092] In some other embodiments, the specific composition of the housing structure 100 can be adaptively adjusted so that the diaphragm structure 121 is located between the first cavity 101 and the second cavity 102 and the measurement requirements are met.

[0093] In some embodiments of the present application, a drain port 123 is provided on the side wall of the intermediate component 120. It is understandable that the drain port 123 can discharge the water input from the first water inlet 111 from the first cavity 101 in time to reduce the influence on the measurement.

[0094] In some embodiments of the present application, a plurality of second water inlets 131 are provided, and each second water inlet 131 is distributed in an array on the bottom plate 130. It can be understood that a plurality of holes are provided on the bottom plate 130 so that the second water inlets 131 are distributed in an array, so that the bottom plate 130 is provided as a porous structure at the bottom of the shell structure 100.

[0095] It should be noted that this application is based on the relevant characteristics of fiber Bragg grating (FBG) and 3D molten deposition technology, and adopts a combined design of an upper cantilever beam structure and a lower diaphragm structure 121, which are used to measure wave impact loads and hydrostatic pressure, respectively, thereby improving the measurement accuracy and applicability of the sensor. At the same time, the fiber grating sensor is not affected by corrosive environments such as seawater, is suitable for use in marine environments, has high sensitivity, and can accurately measure wave impact force and hydrostatic pressure. In addition, the use of molten deposition technology as the packaging technology of the sensor enhances the durability and stability of the sensor.

[0096] Reference Figures 1 to 5 The method for manufacturing a fiber Bragg grating pressure sensor of the second embodiment of the present application may be the method for manufacturing a fiber Bragg grating pressure sensor of the first embodiment of the present application, and the method for manufacturing a fiber Bragg grating pressure sensor comprises the following steps:

[0097] A model is established by using 3D software, and the shell structure 100, the diaphragm structure 121, and the equal-strength cantilever beam structure 200 are printed out by 3D printing;

[0098] Paste the first fiber grating assembly to the center of the upper surface of the equal-strength cantilever beam structure 200, and paste the second fiber grating assembly to the center of the lower surface of the diaphragm structure 121;

[0099] Leading the first fiber Bragg grating assembly and the second fiber Bragg grating assembly out of the housing structure 100;

[0100] The packaging process is performed to seal the inside of the device.

[0101] It is understandable that the present application is made using 3D fused deposition technology, which greatly increases the service life and solves the corrosion problem. In some embodiments, the 3D fused deposition technology used in the present application uses molten plastic filaments (polylactic acid PLA) to accumulate layer by layer through a 3D printer nozzle to print the desired shape.

[0102] In some embodiments, the structure is disc-shaped and consists of three parts. First, the model is established in the modeling software, and then each part is processed by 3D fused deposition printing technology. After the fiber Bragg grating is pasted on the model, the structure is encapsulated with epoxy resin. Its upper structure is a disc-shaped cover plate 110, and the hole is a water inlet for measuring wave impact load. The middle structure is composed of an equal-strength cantilever beam structure 200 and a disc at the bottom of the cantilever beam. The fiber Bragg grating is attached to the upper surface of the equal-strength cantilever beam with epoxy resin along the center line near the middle. The front end of the cantilever beam is a cylindrical structure 210, which is used to receive wave impact and transmit it to the fiber Bragg grating on the equal-strength beam to measure the wave impact force. The fiber Bragg grating is pasted in the middle position of the lower part of the disc. After the 3D fused deposition printing is completed, the fiber Bragg grating is pasted on the lower surface of the disc center for measuring hydrostatic pressure. The lower structure is a disc-shaped porous structure, which is a water inlet for measuring hydrostatic pressure.

[0103] In some embodiments, the elastic modulus of 3D printing material polylactic acid PLA is E=2500MPa, Poisson's ratio v=0.35, density is 1.2g / m^2, wave pressure is 150KPa, the contact area of ​​the disk is about 1〖cm〗^2, then the wave impact force is 15N, the width B of the equal strength beam is 28mm, the length L is 40mm, the thickness h is 8mm, the calculated limit strain is ε=803.57με, and the theoretical sensitivity is 5.36με / KPa. The thickness h of the lower structure diaphragm is 2mm, and the diaphragm radius R is 4cm.

[0104] Reference Figures 1 to 5 The method for using the fiber Bragg grating pressure sensor of the third aspect of the present application, the method for making the fiber Bragg grating pressure sensor may be the method for using the fiber Bragg grating pressure sensor of the first aspect of the present application, and the method for using the fiber Bragg grating pressure sensor comprises the following steps:

[0105] The first fiber grating assembly includes a first optical fiber line 310 and a first grating optical fiber FBG320 and a second grating optical fiber FBG330 arranged on the first optical fiber line 310. The first optical fiber line 310 is arranged on the equal-intensity cantilever beam structure 200 so that the first grating optical fiber FBG320 is arranged near the middle position of the vertical center line of the equal-intensity cantilever beam structure 200, and the second grating optical fiber FBG330 is arranged near one end of the equal-intensity cantilever beam structure 200. The second fiber grating assembly includes a second optical fiber line 410 and a third grating optical fiber FBG420. The third grating optical fiber FBG420 is arranged near the center position of the diaphragm structure 121, and the second optical fiber line 410 is connected to the third grating optical fiber FBG420.

[0106] Design principle based on fiber Bragg grating:

[0107]

[0108] Where λ is the initial wavelength of the fiber Bragg grating under strain-free conditions, Δλ is the drift of the fiber Bragg grating center wavelength caused by strain and temperature changes; P eff =0.22 is the photoelastic coefficient, α and ξ are the thermal expansion coefficient and thermo-optic coefficient of the fiber Bragg grating;

[0109] The principle of measuring wave impact load based on the equal strength cantilever beam structure 200:

[0110] Theoretical formulas for equal strength beam structures include:

[0111] The uniformly distributed load on the structure is simplified to the concentrated force acting on the cylinder at the other end of the equal-strength cantilever beam structure 200, that is:

[0112] F=P×πr 2 #(2)

[0113] F is the equivalent value of the uniformly distributed load applied to the top of the cantilever beam, P is the surface pressure of the cylinder at the top of the cantilever beam, and r is the radius of the cylindrical sensing structure;

[0114] From material mechanics, we know that:

[0115]

[0116] M (x) =-F(Lx)#(4)

[0117]

[0118] According to the boundary conditions ω=0, ω′=0, we can get:

[0119] c1=c2=0

[0120]

[0121] Therefore, the free end deflection of the beam is:

[0122]

[0123] The strain on the beam is:

[0124]

[0125] In the above formula, L is the length of the beam, b is the width of the beam, h is the thickness of the beam, and E is the Young's modulus of the material;

[0126] Combining (1) and (6), the relationship between the hydrodynamic pressure and the FBG wavelength drift under external load is obtained as follows:

[0127]

[0128] So we can know the sensor sensitivity coefficient K PA for:

[0129]

[0130] According to mechanical theory, the radial strain generated at the center of a laterally unconstrained uniform diaphragm under the action of uniform external pressure P is expressed as:

[0131]

[0132] Where, E is the elastic modulus of the diaphragm in the vertical direction; v is the Poisson's ratio; h is the thickness of the diaphragm; R is the radius of the diaphragm;

[0133] The relationship between wavelength shift and hydrostatic pressure is expressed as follows:

[0134]

[0135] Therefore, when the room temperature is stable, the sensor sensitivity coefficient K PB for:

[0136]

[0137] The data measured by the second grating optical fiber FBG330 are used to perform temperature compensation on the data measured by the first grating optical fiber FBG320 and the third grating optical fiber FBG420.

[0138] It can be understood that the third grating fiber FBG420 is encapsulated in the diaphragm, and the diaphragm structure 121 is used to measure the hydrostatic pressure, and the fiber Bragg grating at the root of the equal strength beam is used for temperature compensation. Therefore, according to the basic principle of fiber Bragg grating, it can be known that the second grating fiber FBG330 is strain-free, and the data measured by the second grating fiber FBG330 can be used to perform temperature compensation on the data measured by the first grating fiber FBG320 and the third grating fiber FBG420.

[0139] In some embodiments, after the sensor parameters are defined based on the above-mentioned usage method, the sensor model is established in the 3D modeling software. After the model is processed by the slicing software, each structure is printed out by a 3D printer, including the cover plate 110, the middle structure and the lower porous structure. The fiber Bragg grating is pasted on the center line of the upper surface of the equal-strength cantilever beam and the lower surface of the center of the disk, the optical fiber is led out through the upper and lower optical fiber lead-out ports, and finally the three-part structure is encapsulated with epoxy resin.

[0140] In some embodiments, the FBG (fiber Bragg grating)-based dynamic and static water pressure sensor of the present application uses a cantilever beam structure to measure wave impact loads, and uses a diaphragm structure 121 to measure hydrostatic pressure. The sensor is printed and manufactured using 3D molten deposition technology. The sensor uses FBG sensing technology, so that the sensor is not subject to electromagnetic interference during use. At the same time, the sensor also has the advantages of simple structure and high sensitivity. The use of 3D molten deposition technology greatly increases the service life and solves the corrosion problem. The basic principle of FBG is to introduce periodic refractive index modulation in the core of the optical fiber to form a grating structure. The periodic refractive index change of this grating structure causes Bragg reflection of the optical signal at a specific wavelength. This characteristic makes FBG widely used in fields such as optical fiber communication, optical fiber sensing and optical fiber lasers. 3D printing technology is a manufacturing method that creates a three-dimensional object by stacking materials layer by layer. Unlike traditional subtractive manufacturing methods, 3D printing is a processing method that builds objects by adding materials, thereby achieving advantages such as high customization, complex geometry and rapid prototyping. The 3D fused deposition technology adopted in the present invention uses molten plastic filaments (polylactic acid PLA) to accumulate layer by layer through a 3D printer nozzle to print out a desired shape.

[0141] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0142] The embodiments of the present application are described in detail above in conjunction with the accompanying drawings, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present application.

Claims

1. A fiber Bragg grating pressure sensor, characterized in that: include: Shell structure; A diaphragm structure, the diaphragm structure is arranged in the shell structure, and the diaphragm structure is used to divide the shell structure into a first cavity and a second cavity adjacent to each other in upper and lower directions; a first water inlet, the first water inlet being arranged on the top of the housing structure and communicating with the first cavity; An equal-strength cantilever beam structure, one end of which is arranged on the inner wall of the first cavity, and the other end of which is cantilevered and located at the first water inlet; a second water inlet, the second water inlet being disposed at the bottom of the housing structure and communicating with the second cavity; A first fiber Bragg grating component, wherein the first fiber Bragg grating component is arranged on the equal strength cantilever beam structure so that the first fiber Bragg grating component can be used to measure wave impact load; A second fiber grating component is provided on the diaphragm structure so that the second fiber grating component can be used to measure hydrostatic pressure.

2. The fiber Bragg grating pressure sensor according to claim 1, characterized in that: The first fiber grating assembly includes a first optical fiber line and a first grating optical fiber FBG and a second grating optical fiber FBG arranged on the first optical fiber line. The first optical fiber line is arranged on the equal-intensity cantilever beam structure so that the first grating optical fiber FBG is arranged close to the middle position of the vertical center line of the equal-intensity cantilever beam structure, and the second grating optical fiber FBG is arranged close to one end of the equal-intensity cantilever beam structure.

3. The fiber Bragg grating pressure sensor according to claim 2, characterized in that: The shell structure is formed with a first lead-out port communicating with the first cavity, the isostrength cantilever beam structure is formed with a groove extending along a vertical center line, and the first optical fiber is arranged in the groove and led out from the first lead-out port.

4. The fiber Bragg grating pressure sensor according to claim 1, characterized in that: The other end of the equal-strength cantilever beam structure comprises a cylindrical structure. The cross-sectional shape of the first water inlet is circular. The cylindrical structure extends into the first water inlet and there is a gap between the cylindrical structure and the first water inlet.

5. The fiber Bragg grating pressure sensor according to claim 1, characterized in that: The second fiber grating assembly includes a second optical fiber and a third grating optical fiber FBG. A second lead-out port connected to the second cavity is formed on the shell structure. The third grating optical fiber FBG is arranged near the center of the diaphragm structure. The second optical fiber is connected to the third grating optical fiber FBG and is led out from the second lead-out port.

6. The fiber Bragg grating pressure sensor according to claim 1, characterized in that: The shell structure includes a cover plate, an intermediate component and a bottom plate, the diaphragm structure serves as the bottom of the intermediate component, the intermediate component forms the first cavity and the top is used to assemble with the cover plate, and the bottom of the intermediate component is used to assemble with the bottom plate to enclose the second cavity.

7. The fiber Bragg grating pressure sensor according to claim 6, characterized in that: The side wall of the intermediate component is provided with a drainage port.

8. The fiber Bragg grating pressure sensor according to claim 6, characterized in that: A plurality of the second water inlets are provided, and the second water inlets are distributed on the bottom plate in an array.

9. A method for manufacturing a fiber Bragg grating pressure sensor according to any one of claims 1 to 8, characterized in that: The following steps are involved: Build a model through 3D software, and print the shell structure, diaphragm structure, and equal-strength cantilever beam structure through 3D printing; Paste the first fiber grating assembly to the center of the upper surface of the equal-strength cantilever beam structure, and paste the second fiber grating assembly to the center of the lower surface of the diaphragm structure; Leading the first fiber grating assembly and the second fiber grating assembly out of the housing structure; The packaging process is performed to seal the inside of the device.

10. A method for using the fiber Bragg grating pressure sensor according to any one of claims 1 to 8, characterized in that: The following steps are involved: The first fiber grating assembly includes a first optical fiber line and a first grating optical fiber FBG and a second grating optical fiber FBG arranged on the first optical fiber line, the first optical fiber line is arranged on the equal-intensity cantilever beam structure, so that the first grating optical fiber FBG is arranged close to the middle position of the vertical center line of the equal-intensity cantilever beam structure, and the second grating optical fiber FBG is arranged close to one end of the equal-intensity cantilever beam structure, the second fiber grating assembly includes a second optical fiber line and a third grating optical fiber FBG, the third grating optical fiber FBG is arranged close to the center position of the diaphragm structure, and the second optical fiber line is connected to the third grating optical fiber FBG; Design principle based on fiber Bragg grating: Where λ is the initial wavelength of the fiber Bragg grating under strain-free conditions, Δλ is the drift of the fiber Bragg grating center wavelength caused by strain and temperature changes; P eff =0.22 is the photoelastic coefficient, α and ξ are the thermal expansion coefficient and thermo-optic coefficient of the fiber Bragg grating; The principle of measuring wave impact load based on equal strength cantilever beam structure: Theoretical formulas for equal strength beam structures include: The uniformly distributed load on the structure is simplified to the concentrated force acting on the cylinder at the other end of the cantilever beam structure with equal strength, that is: F=P×πr 2 #(2) F is the equivalent value of the uniformly distributed load applied to the top of the cantilever beam, P is the surface pressure of the cylinder at the top of the cantilever beam, and r is the radius of the cylindrical sensing structure; From material mechanics, we know that: M (x) =-F(L-x)#(4) According to the boundary conditions ω=0, ω′=0, we can get: c1=c2=0 Therefore, the free end deflection of the beam is: The strain on the beam is: In the above formula, L is the length of the beam, b is the width of the beam, h is the thickness of the beam, and E is the Young's modulus of the material; Combining (1) and (6), the relationship between the hydrodynamic pressure and the FBG wavelength drift under external load is obtained as follows: So we can know the sensor sensitivity coefficient K PA for: According to mechanical theory, the radial strain generated at the center of a laterally unconstrained uniform diaphragm under the action of uniform external pressure P is expressed as: Where, E is the elastic modulus of the diaphragm in the vertical direction; v is the Poisson's ratio; h is the thickness of the diaphragm; R is the radius of the diaphragm; The relationship between wavelength shift and hydrostatic pressure is expressed as follows: Therefore, when the room temperature is stable, the sensor sensitivity coefficient K PB for: The data measured by the second grating optical fiber FBG are used to perform temperature compensation on the data measured by the first grating optical fiber FBG and the third grating optical fiber FBG.

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